dash, n.² — Green’s Dictionary of Slang

dash n.²

[SE dashee, a gift, present, gratuity; a ‘Negrish word’ used on the Guinea Coast]

a tip, bribery, the money paid as a bribe.

1937–84		Partridge DSUE (1984) 292/1: from ca. 1780.
1981		W. Boyd ‘The Coup’ in On the Yankee Station (1982) 158: He said good-bye to Isaac, and Moses his cook [...] He’d given them all a sizeable farewell dash the previous evening.
1989		J. Morton Lowspeak 47: Dash – originally a gratuity but now a bribe.